Question

Which term of the AP:125,121,117,.. is the 1st negative term?

Answer 1

Let x be the first negative term

a=125

d=121-125=4

n th term is a+(n-1)d

==> x <0

==> a+(n-1)d<0

==> 125-4n+4<0

==> 129<4n

==>The smallest possible value of n is 33

for which 132>129

Thus x is the 33rd term

a+(n-1)d

=125-4n+4

n=33

=129-132

=-3

Hence -3 is the first negative term.

Hope it helps

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